The present invention relates to a method for producing a motion picture screen and more particularly to a method for producing a motion picture screen which makes it possible to provide easily and with accouracy a motion picture screen influenced little by surrounding light.
In motion picture screen technology many attempts have been made to provide a screen which is of high brightness. The brightness of a motion picture screen on its front surface has been increased in general by the use of various materials on the surface and treating it so as to have fine roughness so that a surface which can concentrate a quantity of light in a narrower angle range is obtained. A known surface having minute roughness utilizes random and fine surface roughness obtained by a rolling of a thin sheet, or one as shown in FIG. 1 of the attached drawings, wherein FIGS. 1a, b and c represent plan, cross-sectional and longitudinal sectional views, respectively. The screen shown in FIG. 1 has a surface which has a number of minute rugged elements, the reference 1 representing the surface thus formed.
As another, conventional, motion picture screen, also shown in FIG. 2 in perspective view there is known one wherein both sides including the reflecting surface 1 respectively have a number of rugged elements which orthogonally intersect each other, which elements can be machined using a conventional one-dimensional cutter. However, in the screens shown in FIGS. 1 and 2, since the rugged elements of the reflecting surface 1 have respectively an irregular shape, and the adjoining elements are not connected by a smooth surface, there being acute angle portions therebetween, the directional reflection quality is inferior, resulting in a decrease in contrast and colour reproduction when a projector having a low light intensity is used, or the screen is used under circumstances which allow light to be projected onto the periphery thereof. Therefore, conventional motion picture screens have a defect that in order to be used most effectively they must be used in a substantially dark environment.
Motion picture screens of this kind or the like are also disclosed in the following U.S. patents. In U.S. Pat. No. 3,263,561 to J. G. Jackson high light reflecting screens are disclosed which comprise a plurality of individual substantially rectangular main reflectors which together form a reflecting surface for the screen, each of the main reflectors being curved from the four sides thereof towards the center out of the general plane of the reflecting surface. However, nothing is referred to therein as to the use of a two-dimensional cutter as well as the carrying out of a relative movement between it and a workpiece when the screen is to be produced from the workpiece with its surface being machined by the cutter.
Further, in U.S. Pat. No. 2,961,926 reflective devices having multi-curved surfaces are disclosed, and they are said to be produced by the use of a board provided with a lower edge shaped according to a wavy line. Although this board resembles the two-dimensional cutter used in the present invention the reflective devices of this U.S. Patent are not a motion picture screen, and the configuration of their waved surface does not substantially conform to that of the screen surface produced by the method according to the present invention.